Abstract: The design and practice in supporting the cut slope of an open-pit mine were introduced, in which the high pressure grouting method was used in reinforcing the weak formation in the slopes. Based on a detailed geological survey of the slope, a theoretical analysis was carried out, and the design parameters were proposed, where the Tresca or Mohr-Coulomb yield criteria was employed. A patent technology, named "Technology of high pressure and multiple grouting in different levels within a single hole", was employed in the construction. Anchor bars were also installed as grouting proceeds. This method combines anchoring and grouting comprehensively and was found successful in practice.